1. Field of the Invention
The present invention generally relates to olive oil production and more specifically to olive oil production at a prolonged time after olive harvesting.
2. Discussion of the Related Art
Olive oil is produced by grinding fresh olives into a paste and extracting the oil from the paste by mechanical or chemical means. The amount of oil contained in the olive depends on the particular cultivar and the degree of ripeness. Typically 1 Kg of olives yields about 150-200 ml of oil. The oil is accumulated in the mesocarp cells, mostly in the vacuoles and to a smaller extent in the cytoplasm. Grinding or crushing of the olives breaks the olive stones and flesh, creating a paste. Typically, grinding is followed by malaxation of the paste to facilitate breaking of the mesocarp cells, assisted by the sharp stone segments, thus releasing the oil contained in the vacuoles and resulting in coalescence of the oil droplets and separation of the liquids from the solids. The liquid, which contains both oil and vegetation water, is extracted from the paste by applying pressure or centrifugation and is then separated into oil and water. Depending on the specific method and equipment, the separation of the paste into liquid and solid and the separation of the liquid into oil and water may be performed sequentially or concurrently. There exist various modifications of these basic steps. For example, the method known as “Sinolea” is based on the different surface tension of the vegetable water and the oil. According to this method, rows of metal discs or plates are dipped into the paste. The oil adheres to the metal disks and is removed with scrapers in a continuous process while the solid and water phases stay behind.
The quality of olive oil depends on the extraction method, the olive cultivar, the maturity (ripeness) index of the olives and also, to a great extent, on the time delay between olive harvest and oil extraction. Because olive oil is extracted from the fruit flesh, the time elapsing from harvesting to oil extraction is very crucial. In the period between harvesting and oil extraction, the fruits' enzymes are very active. The oxidation and enzymatic reactions, which begin in the fruit immediately upon harvesting, increasingly degrade the quality of the oil. Therefore, olive oil needs to be extracted from the fresh harvested olives as soon as possible, preferably within no more than 24 hours. Oil obtained after a longer wait is of lower quality presenting higher acidity levels. Thus, unlike seed oils (e.g. sunflower oil, sesame oil, soybeans oil, etc.) which are extracted from seeds or nuts that can be stored for prolonged time and processed all year round, the olive oil industry is a seasonal industry which depends on availability of fresh olives. Harvesting time varies in each country and with the season and the cultivar. Generally, fresh olives are available for about four months during opposing seasons in the Northern and Southern hemispheres (October to January in the Northern Hemisphere and April to July in the Southern hemisphere). Another important factor that influences the oil quality is the freshness of the olive oil itself, namely the storage period and the storage conditions until consumption. Olive oil, even when stored under optimal conditions, deteriorates over time. It is therefore recommended to consume olive oil close to its production time.
The quality of olive oil can be characterized by various analytic and organoleptic parameters, the most common being the free fatty acid (FFA) expressed as percent of oleic acid. Other characteristics include peroxide value and various positive and negative organoleptic attributes. Most countries use the International Olive Council (IOC) standards for defining oil quality and oil category. The IOC, which has a United Nations charter to develop criteria for olive oil quality and purity, consolidates standards for olive oils categories as well as guidelines for analyzing and tasting the oils. For example, olive oils that can be qualified under the category of virgin olive oils are oils that are obtained from the olives by using only mechanical or other physical means which do not involve any chemical processes such as use of solvents or re-esterification. Additionally, they should meet the specific standards set by the IOC with regard to the concentration of specific ingredients and organoleptic tests. Within the Virgin Olive Oil category, the oils fit for consumption are classified as Extra Virgin Olive Oil, Virgin Olive Oil and Ordinary Virgin Olive Oil according to their FFA level (≦0.8%, ≦2% and ≦3.3, respectively).
Olive oil production is a traditional industry originating in the Mediterranean and known since as early as 3,000 B.C. Today, olives are cultivated in many regions of the world and olive oil is used throughout the world. However, olive oil production and consumption is still the highest in the Mediterranean. The oil is considered to be a prime component of the so called ‘Mediterranean diet’.
In recent years, the olive oil market has been growing dramatically. The increasing interest in olive oil stems from both its unique rich taste and its health benefits and coincides with the growing public awareness to health food, as well as with the general increasing interest in gourmet food. The health benefits associated with olive oil consumption include controlling LDL level while raising HDL level and reducing risk of coronary heart diseases. These health benefits are attributed to the high level of monounsaturated fatty acids, mainly oleic acid, and to the relatively high content of minor nutrients, in particular anti-oxidants such as polyphenols. Studies also suggest beneficial effects of olive oil consumption on blood sugar level and on the gastrointestinal tract, including reducing the risk of ulcers, gastritis and colon cancer. Indeed, olive oil is considered by many to be superior to other vegetable oils. However, side by side with the prosperity in the olive oil market, the olive oil fraud industry flourishes as well. Olive oil is one of the most adulterated agricultural products. Customers are therefore becoming increasingly aware of the possibility that oil distributed as high quality olive oil is actually adulterated oil mixed with, or even consists almost entirely of, inferior oils of lower cost.
The awareness to health food products, as well as to their freshness and authenticity, has brought with it a new trend of small scale production of basic food products (e.g. bread) for self consumption at home or in small food establishments such as restaurants, delicatessen and specialized boutiques. This way control over freshness and ingredients is ensured. In accordance with this trend, small scale appliances, sized to be placed on a kitchen counter, such as bread machine, home-use coffee roasting device, etc., are now gaining popularity. With respect to olive oil, recent years show an increasing number of olive oil boutiques which specialize in production of high quality oil by careful selection of olives and close control over production. A household countertop cold press machine for producing small quantities of olive oil designed by the inventors of the present invention is described in international publication WO2010/007610. However, although olive oil can be consumed as is when freshly pressed from the fruit, the need to extract olive oil within a very short time from harvesting does not enable producing olive oil out of season or in countries distant from olive growing regions.
It is therefore the general object of the present invention to provide olives suitable for oil extraction all year round and/or at locations remote from olive growing regions.
In particular, it is all object of the invention to provide olives which retain their oil qualities for a prolonged storage period without adding chemical food preservatives.
It is a further object of the invention to provide methods for treating freshly harvested olives to substantially retain their oil quality for a prolonged time after being treated so as to enable extraction of high quality oil from the olives at a prolonged time after they have been harvested.